Biomass is an increasingly important raw material for fuel and industrial chemical production. Cellulose present in most biomass sources can be especially difficult to render accessible to reaction. In addition, many processes directed to converting biomass to fuel or industrial chemicals are limited in production capacity because the rate at which biomass is processed is low. Further, many processes for biomass conversion are directed to making a single product such as ethanol or butanol.
Some methods for processing biomass utilize a supercritical fluid. Supercritical fluids have been used in a number of ways.
Supercritical solvents such as supercritical water (SCW) and supercritical carbon dioxide (SCCO2) have been used in extracting various substances and assisting chemical reactions. For example, U.S. Pat. No. 5,516,952 presents a process for breaking down natural, synthetic, vulcanized, and non-vulcanized rubbers. Typical products were said to include alkanes, alkenes, dienes, aromatics, alcohols, carboxylic acids, aldehydes, and ketones, all preferably having from about 3 to about 8 carbon atoms, as well as carbon dioxide, water, and halide acids. U.S. Pat. No. 5,830,763 describes a process for the preparation of organic and inorganic deuterium-tagged compounds by heating with deuterium oxide under supercritical conditions. U.S. Pat. No. 6,180,845 describes a process for the fractionation of waste biomass into a hydrocarbon mixture. U.S. Pat. Nos. 4,543,190 and 4,338,199 describe processes for the oxidation of organic compounds in supercritical water.
D. Boocock et al., “Liquefaction of biomass by rapid hydrolysis” Can. J. Chem. Eng., 61:80 (1983) discloses the use of supercritical water to liquefy the biomass.
Peter et al., “High pressure extraction of lignin from biomass” Supercritical fluid technology, p. 385 (1985) discloses the use of supercritical fluids to get the lignin from biomass but not cellulose and xylose.
Houghton et al., “Reactivity of some organic compounds with supercritical water” Fuel, 61:827 (1986) discloses the use of supercritical fluids to decompose the organic compounds.
Modell et al., “Supercritical water oxidation of pulp mill sludges” TAPPI J., 75:195 (1992) discusses the use of supercritical water for the oxidation of pulp mill sludges.
B. Potic et al., “Gasification of Biomass model compound and real biomass in Supercritical Water,” Biomass and Bioenergy, 26:71-78 (2004); F. C. Knopf et al., “Reactive Extraction of Lignin from biomass using supercritical ammonia-water mixtures” J. Supercritical Fluids, 6:249-254 (1993); B. J. McCoy et al., “Extraction of Lignin from biomass with supercritical alcohol” J. Supercritical Fluids, 2:80-84 (1989); and B. Bennett et al., “Chemicals from forest products by supercritical fluid extraction” Fluid Phase Equil., 10:337 (1983) also provide further background information on use of supercritical fluids.
Methods for efficiently converting biomass from renewable resources or waste materials to more valuable products are desirable.